{"id":"F2006B04581","name":"AD/BELL 212/49 - Tail Rotor Driveshaft Hangar Bearings","slug":"ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114314,"registerId":"commonwealth-F2006B04581-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 212/49 - Tail Rotor Driveshaft Hangar Bearings","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Bell Helicopter Textron 212 Series Helicopters\n\n \n\nAD/BELL 212/49 Tail Rotor Driveshaft Hangar Bearings 1/92\n\nDM\n\n \n\nApplicability: All models fitted with tail rotor driveshaft bearings.\n\n \n\nP/N 204-040-623-003 with a S/N prefix of either “T” or “N” prior to N4000 and all - 005 bearings with a S/N prefix of either “T” or “N”.\n\n \n\nRequirement: Action in accordance with Bell Alert Service Bulletin 212-91-69 Revision A.\n\n \n\nNote: FAA Priority Letter AD 91-24-16 refers.\n\n \n\nCompliance: Daily before first flight of the day after 27 November 1991.\n\n \n\nBackground: A daily inspection of the tail rotor driveshaft bearings has been found necessary following a fatal accident which revealed the possibility of a production batch problem with these bearings.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive as published sets a narrow, clearly stated scope: specified bearing part/serial numbers on Bell 212 helicopters and a single mitigative action (daily inspection per the Bell Alert Service Bulletin). The text contains no indication that the scope was altered from any prior version; it targets a specific subset of bearings and prescribes a single operational requirement."},"complexity_factors":["Targeted technical scope: specific part numbers and serial‑number prefixes (P/N 204-040-623-003 with S/N prefix “T” or “N” prior to N4000; all -005 bearings with S/N prefix “T” or “N”) (Applicability clause).","Operational timing requirement: daily inspection before first flight after 27 November 1991 (Compliance clause).","Dependence on an external document for the required action: Bell Alert Service Bulletin 212-91-69 Revision A (Requirement clause).","Safety‑critical nature increases operational impact despite simple wording (Background: fatal accident and possible production batch problem).","Regulatory cross‑reference: notes FAA Priority Letter AD 91-24-16, implying coordination with foreign regulator guidance (Note)."],"plain_english_summary":"Mandates a daily pre‑flight inspection of tail‑rotor driveshaft hangar bearings on Bell 212 helicopters fitted with specified part and serial‑number bearings, carried out per Bell Alert Service Bulletin 212‑91‑69 Rev A. Compliance was required for the first flight after 27 November 1991. The rule affects Bell 212 operators who must absorb inspection time, recordkeeping and any replacement costs. The action was prompted by a fatal accident indicating a possible production‑batch defect."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive responding to a specific known defect. It has not expanded beyond its original purpose of mandating daily inspections for a specific bearing production batch issue identified after a fatal accident."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined part number/serial number combinations to identify affected bearings","Single, clear compliance action (daily inspection)","No cross-references to other legislation sections","No conditional logic or exceptions","Straightforward applicability test based on physical part markings"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on aircraft.\n\n**What it does:** It orders owners and operators of **Bell 212 series helicopters** to perform a **daily inspection of the tail rotor driveshaft hangar bearings** before the first flight each day.\n\n**Who it affects:** Anyone operating Bell 212 helicopters fitted with specific part numbers of these bearings:\n- Part number 204-040-623-003 with serial numbers starting with \"T\" or \"N\" (before N4000)\n- All part number -005 bearings with serial numbers starting with \"T\" or \"N\"\n\n**Why it matters:** A **fatal accident** revealed that some bearings from certain production batches could fail. This daily check is designed to catch potential bearing problems before they cause another accident. The directive references a Bell Alert Service Bulletin and a US FAA directive, showing this is part of an international safety response.\n\n**When compliance started:** From 27 November 1991, these checks became mandatory every day before the first flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings","history":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings/history","analysis":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings/analysis","conflicts":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings/conflicts","importantCases":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings/important-cases","documents":"/api/acts/ad-bell-212-49-tail-rotor-driveshaft-hangar-bearings/documents"}}